Electrical fixtures and telephones in dwellings, offices and commercial buildings are very often installed on levels other than that of the power source location, and the running of wire in cavities behind wall finishes or concealed in void spaces of framed partitions is the most commonly accepted method of installation. The installer drills holes or cuts small access openings in the partitions on lower and upper levels, inserts a weighted line in the partition aperture at the upper level, drops the line an approximated distance to the lower level, returns to the lower level and attempts to snare and retrieve the line through the small hole in the lower partition. In the electrical trade, this procedure is commonly referred to as "fishing" or "to fish".
The currently applied methods of fishing for wiring lines depends largely on guesswork and is not a very efficient or easy task, even for the experienced mechanic. Many problems occur with tangled lines, misaligned holes, the need for installer assistance or repetitive trips between levels by the installing mechanic, larger than necessary holes in partitions, poor workmanship, costly repair work, and loss of time and labor.
In an apparent attempt to overcome some of the problems associated with conventional fishing techniques, a fishing device has been proposed which includes a magnet and a magnetically attractable sensor. This device, which is described in U.S. Pat. No. 3,078,073, is not, however, practical for several reasons. Firstly, the magnetic sensor is relatively small. As a result, when the device is being used, the mechanic must know to almost a certainty the exact distance between the hole into which the magnet is placed and the position above the magnet from which the sensor is suspended. If the line suspending the sensor is two or three inches longer than the distance between the lower hole and the attic or other place from which the sensor is suspended, the sensor will not be attracted by the magnet. Instead, the flexible line, which is not attracted to the magnet, will be in the vicinity of the magnet and accordingly the mechanic will have no idea that he is even close to the magnet. Secondly, the magnet of the patented device is mounted in a small holder which is adapted to be secured to a conductor of an electrical cable. After the conductor is screwed onto the magnet holder, the holder and conductor are inserted into the lower hole in the wall. This arrangement may be satisfactory when a relatively rigid cable is used but is totally unsatisfactory when a thin, flexible cable such as a telephone line is being installed. If a thin, flexible wire were attached to the magnet holder and inserted into the hole in the wall, the holder would hang vertically with the magnet facing downwardly in an inoperative position. And thirdly, the patented device, being comprised essentially of two entirely separate parts without a housing or container therefor, makes it difficult to carry in a tool box or the like and makes it possible to easily loose one of these two parts.
The present invention provides a tool which can be used to eliminate or reduce the stated problems now encountered by mechanics in the process of fishing for wiring lines. In addition the use of the invention enables the novice to be as proficient as the experienced mechanic.
One main feature of the invention is to allow the mechanic, while on the upper level, to accurately position the line at the desired location on the lower level, thereby eliminating time consuming guesswork and chance of present methods. Prescribed use of the tool of the present invention enables the mechanic to sense by feeling, and very often by the sound, of parts making contact. Optimum efficiency and certain precision are achieved by the user knowing which part of the sensor assembly is engaged with the magnet. Another main feature of the invention is that much time and labor are saved at the lower floor level, by providing a sensor assembly that can be engaged by the forces of magnetic attraction, manipulated into alignment with and advanced into partition holes having minimized dimensions, and withdrawn for snaring an attached wiring line. With the invention, problems encountered in fishing for electrical wiring lines are substantially eliminated or reduced, with resultant savings in labor and time.